Method and apparatus for cold joining flanges and couplings elements to pipes

ABSTRACT

A method for joining flanges or other couplings to pipes, wherein a plurality of radially expanding segments ( 10 ) with circular ridges ( 11 ) on a tool inserted into the pipe ( 1 ), press beads ( 5, 6 ) in the pipe wall into corresponding grooves ( 3, 4 ) in the surrounding coupling element ( 2 ), where the pipe end, by means of a projection on the segments, is given an overbending outwards that prevents the pipe end from tapering inwards during the pressing of the beads. The invention comprises the interior configuration of the coupling element as well as a tool for pressing the beads.

The invention relates to a system and a method for joining flanges orother coupling elements to pipes and a tool for performing the method.

Flanges of many types and varieties are used extensively in industrywhen pipe-to-pipe or pipe-to-other component connections are to beprovided. The welding of flanges to pipes is the most common method inthe case of steel pipes and standard weldable metals, whilst, forexample, screw flanges are used in connection with, for instance,galvanised pipes.

In recent years a number of methods have been developed for thefastening of coupling elements and the joining of pipes by deforming thepipe inside the coupling so as to secure it. Other methods and equipmentwhich clamp the coupling to the outside of the pipe without any or withlittle deformation of the pipe have also been developed. Examples ofsuch methods are taught in U.S. Pat. No. 4,593,448 and U.S. Pat. No.4,147,385. DE 27 24 257 and U.S. Pat. No. 2,252,274 teach tools withrollers which by means of a rotating cone in the centre with rollerstherearound will deform the pipe so that it fits into grooves in thecoupling elements. DE 3144385 teaches a joining system for pipes whereradially movable ridges, with the aid of hydraulic pressure againstunderlying pistons, press in beads. However, as discussed further below,the pipe wall on the side of the beads will buckle inwards, and when theridges of the tool are retracted, the actual bead in the pipe will alsoretract somewhat, which makes the connection weak. In addition, therewill be a metal-to-metal seal between pipe and coupling element, andtherefore the system taught in the said document will require sealingmaterial in the grooves of the coupling element. It has been found thatwith radial pistons as taught in DE 3144385 it is not possible to obtainan especially large radial force, and this principle could perhaps beused with particularly thin-walled pipes.

To deform a pipe wall into grooves in a surrounding coupling elementrequires very large forces if the pipe wall is to be pressed radiallyoutwards. The use of rollers as described in DE 27 24 257 and U.S. Pat.No. 2,252,274 means that less radial force is required, but on the otherhand the tool must be secured to the pipe and therefore becomes largeand heavy. Rolling subjects the material to harsher treatment and alsotakes longer than radial pressing.

The object of the invention is to provide a system for joining flangesor other coupling elements to pipes where the tool is only operatedradially so that a fixing of the pipe is not necessary. Furthermore, itis an object to obtain a tool which even in connection with small pipedimensions has enough force to deform beads in relatively thick pipewalls. It is also an object that the tool should function so that inwardtapering of the pipe end, which has been found to be a problem inconnection with the radial pressing of beads, is avoided.

FIG. 1 shows pipe and coupling elements before the beads (5, 6) arepressed in. FIG. 2 shows the same after the beads have been pressed intothe coupling element. FIG. 3 shows a collar pressed into place for aloose flange. FIG. 10 shows a flange having spherical movability.

The principle of the tool is shown in FIG. 5, whilst differentembodiments of the cone used as a mechanical force amplifier are shownin FIGS. 6-8. FIG. 9 shows a tool with a hydraulic force amplifier.

During the development of the invention, which comprises both theinterior configuration of the external coupling element and the toolwhich forms the beads, it was quickly discovered that the most criticalparameter for optimal attachment resides in the configuration of thepart of the tool that presses the beads and also the part of the toolthat is to prevent the end of the pipe from tapering inwards during thepressing operation.

FIGS. 1 and 2 show that the outermost portion (a) of the couplingelement against which the pipe end (b) rests is flared outwards. This isto allow the tool to give the pipe end (b) an overbending outwards,which is necessary because the pipe end, as mentioned, tends to taperinwards. Thus, the pipe is almost straight after the beads (5, 6) havebeen pressed, as can be seen in the enlarged section in FIG. 2.

The same basic interior configuration of the coupling elements willapply to a collar for loose flanges as shown in FIG. 3, sphericallymovable flanges as shown in FIG. 4 and other types which may be suitablefor the same fastening method.

It should be mentioned that the cylindrical part (c) of the couplingelement as shown in FIG. 3 may advantageously be quite thin-walled. To acertain extent, the wall will then be resilient and yield a littleduring the pressing operation, and this will then mean that afterwardsit is under inward tension and thus provides further pressure in theconnection where the pipe is in tension outwards.

Tests carried out in the laboratory show that a mechanically good sealis obtained between the grooves (3, 4) and the beads (5, 6).Nevertheless, it may be appropriate to insert a sealing material in oneor more of the grooves.

According to FIG. 5, the principle of the tool is based on a pluralityof segments (10) having circular ridges (11) being pressed out towardsthe pipe wall and forming the beads first. Towards the end of thepressing operation, the cylindrical part (13) of the segments is pressedagainst the pipe in the portions on the sides of the beads to preventthem from buckling inwards. This process is shown in FIG. 4 a and FIG. 4b as well as in FIG. 11. FIG. 4 a shows the pipe (1) and the coupling(2) before the pressing operation, and FIG. 11 is an enlarged view ofthe intermediate stage during the pressing where the aforementionedbuckled-in areas (b) of the pipe on the side of the beads can be seen.In FIG. 4 b it is seen that the cylindrical portions of the segmentshave pressed the buckled-in areas back towards the coupling element sothat they lie almost flush with the diameter of the pipe. Thisafter-pressing gives a powerful radial tensioning effect in the pipewhich increases the contact pressure between pipe and coupling elementin the sealing points between beads and grooves, and prevents theretraction of the pipe as mentioned above when referring to plain ridgesas previously described in, for example, DE 3144385. Innermost on thesegments there is provided a projection (14) which presses against theend of the pipe. In a corresponding portion of the coupling elementthere is a recess (a) which may be made in the form of a bevel edge or acut-out. This cut-out can, for some uses, be partially filled withsealing material, or it may have an O-ring fitted therein. This specialdesign of the tool and the coupling element has been found to benecessary in order to prevent the pipe from tapering inwards aspreviously mentioned.

The segments (10) and especially the ridges (11) are subjected toextremely large stresses during the pressing operation and are thereforemade of hardened steel. Consequently large radial forces are alsorequired to operate the segments. As an example thereof, the pressing ofa connection of a steel pipe with an outer diameter of 76 mm and a wallthickness of 3.2 mm as shown in FIGS. 2 and 3, with eight segments wouldrequire a radial force per segment of about 200 kN, in total a requiredforce of about 1600 kN. These are huge forces within a very narrowspace, and the tool according to the invention therefore uses a poweractuator outside the pipe combined with a force amplifier inside thepipe.

FIG. 6 shows the tool with a circular cone (20) as force amplifier, FIG.7 shows the tool with the cone drawn in and the segments in expandedposition. FIG. 8 shows the same tool with a polygonal pyramid as forceamplifier.

FIG. 9 shows a tool with hydraulically operated segments where a segment(22) is shown separately and it can be seen that the segment is fastenedto a piston (27) which can move in a corresponding cylinder in thehousing (21) which is filled with oil. In the illustrated tool, therewill thus be a total of eight pistons and eight cylinders. When the rod(25) is pressed into the housing, the oil will press the pistons (27)outwards. The greater the diameter of the piston in relation to thediameter of the rod, the greater the force amplification.

A cold joining of the coupling element of this kind means, unlike, forexample, welding, that the material of the coupling is not given amodified surface structure. Therefore, the invention is suitable forcouplings as shown in FIG. 10 where a spherical coupling element (30) isfastened to the pipe and where a two-part flange (31, 32) is screwedtogether, the two parts facing one another on each side of the couplingelement. The flange will then be capable of being mounted at a variableangle relative to the pipe. It will either be freely movable, even afterscrewing, or will be such that it is locked to the coupling element (30)when the flange is tightened to another flange.

1. A method for joining a coupling element, e.g. a joining flange means,to a pipe, said coupling element surrounding the pipe and having groovesfacing the pipe and intended to receive a corresponding plurality ofbeads provided on the pipe, characterised in the steps of: providingsaid coupling element to surround the pipe at an end region thereof,providing a first and dedicated redial directed pressing action on theinside wall of the pipe at axial locations of the pipe corresponding tolocation of said grooves on the surrounding coupling element to deformthe pipe thereat to create said beads and cause said beads to projectinto said grooves, and providing a second and dedicated radial directedpost-pressing action on the inside wall of the pipe at buckled-inregions of the pipe wall that naturally occur between and adjacent thecreated beads during and caused by the first pressing action, to cause apost-pressing of said regions in an outward direction, thereby providingan outward tension in the pipe at the location of the coupling element.2. A tool for joining a coupling element, e.g. a joining flange means,to a pipe, said coupling element intended to surround the pipe andhaving grooves facing the pipe and intended to receive a correspondingplurality of beads provided on the pipe, characterised in that the toolhas plurality of axially separated, radially movable segments (10), eachsegment having a plurality of circle sector formed ridges, saidplurality of segments thereby providing circumferentially extendingridges (11) capable of deforming the pipe wall by a first pressingaction on the inside wall of the pipe to create on the outside of thepipe circumferential beads (5; 6) in the pipe wall and cause said beads(5; 6) to extend into corresponding ones of said grooves (3; 4) in thecoupling element, and that the segments have circumferentially extendingportions (13) located adjacent and between the ridges, said portions(13) in a second, subsequent passing action to cause post-pressing ofbuckled-in areas that occur naturally in the pipe wall between andadjacent the beads during the first pressing action, so that an outwardtension is obtained in the pipe at the location of the coupling element.3. A tool according to claim 2, characterised in that a part of thesegments which is to lie axially aligned with the end of the pipe has aprojection (14) which is configured to press the pipe end out slightlyfurther than the diameter proper of the pipe
 4. A tool according toclaim 2, characterised in that the segments provide an internal conicalshaped or polygonal pyramid shaped space, and that a cone or polygonalpyramid is locatable internally of and coaxially with the segments, saidcone or pyramid when pulled towards a narrow end of said shape causingthe segments to move radially outwards.
 5. A coupling elementconnectable to a pipe, said coupling element configured to surround thepipe and having grooves to face the pipe and to receive a correspondingplurality of beads provided on the pipe, for use with a tool accordingto claim 2 characterised in that the coupling element at its foremostportion has a recess with a diameter greater than an outer diameter ofthe pipe, so that when the coupling elements surrounds the pipie andsaid recess is aligned with the end of the pipe, that pipe end ispressable into said recess through an outward bending action thereon. 6.A coupling element according to claim 5, characterised in that thecoupling element (30) has a part of its outer surface spherically shapedto allow a two-part flange device with internal space thereof configuredto be clamped to the surface of the coupling element, whereby alongitudinal axis through said two-part flange device is angularlyadjustable relative to a longitudinal axis of the pipe.